1. Field of the Invention
The present invention relates to encoding digital and audio images. More specifically, the present invention relates to an apparatus and a method for decoding digital image and audio information in a digital cinema system. The invention further relates to the encoding, compression, storage, decryption, decompression, decryption, and controlled playback of electronic audio/visual programming from a central facility to multiple display projectors or presentation systems.
2. Description of the Related Art
For several decades, the motion picture industry has depended on the duplication, distribution, and projection of celluloid film for delivering creative programming material to geographically diverse theaters around the country and the world. To a large extent, the methods and mechanisms for the distribution of film material has remained relatively unchanged.
The current film duplication and distribution process is illustrated in FIG. 1. Film duplication typically starts with an exceptional quality camera negative. At a film studio 50, a film editor 52 produces a master film copy after the process for producing the original film has taken place. From this master film copy, a film duplication element 54 produces what is referred as a distribution negative, from which distribution prints (known as “positives”) are produced in quantities. Depending on the size of the release or number of copies desired for distributing the film, there may be more intermediate steps or multiple copies produced at each stage. The film positives are distributed by courier and other physical means to various theaters, as exemplified by a theater 56. At the theater 56, the movie is displayed by projecting images from the film onto a display surface using a film projector 58. In this traditional system, a multiple track audio program is generally created by an audio editing system 51 and printed along with the motion picture images on the film so that this soundtrack can be played back on a theater sound system 57 in time synchronization with the motion picture in a theater projection system.
Although the distribution process shown in FIG. 1 works well, there are inherent limitations. Due to the use of celluloid material for the film and the bandwidth limitations of the film media, there are restrictions on the ability to provide high fidelity multi-channel audio programming. Then, there is the high expense of making a large number of film duplicates, which can cost several hundreds of dollars for each feature length film. There is also the expense, complexity, and delay associated with physically distributing large canisters of celluloid film to a large and growing number of theater locations. Also, a growing trend in the motion picture theater industry is the development of so called “multiplex” theater locations in which multiple projection auditoriums are located or clustered together at a single theater location. Each projection auditorium may show a motion picture at the same time as other motion pictures are being shown in the other projection auditoriums in the multiplex complex.
Because of the large number of duplicates made, it becomes increasingly difficult to prevent illegal duplication and theft of the material. It is estimated that revenues lost due to piracy and theft account for billions of dollars lost each year by the motion picture industry. Further, duplicated film material tends to degrade over time due to dust collection, wear-and-tear, thermal variances, and other known factors. Finally, management cost and other expenses are involved in the eventual destruction of the film material, which may contain regulated hazardous material.
New and emerging technologies are making it possible to provide alternative approaches to the ongoing film distribution problems. For example, satellite transmission methods are now available, although they are not currently commercially viable for the distribution of high quality audio/visual (AV) material. Since the distribution of film programming is essentially a special type of broadcast to a continent-wide region, a satellite distribution method with inherent advantages to such wide area broadcasting would seem ultimately appropriate for film distribution. However, in order to transmit a quality AV signal in “real-time,” the data rate requirement (in bits per second) is on the order of 1.5 billion bits per second. This high data rate requires the capacity equivalent of an entire satellite to transmit even a single program, which is prohibitively expensive. Moreover, alternative distribution technologies have not been able to offer the image quality and projection brightness available using celluloid film. Competing technologies typically involve audio/visual (AV) signals recorded on various magnetic or optical media for display on video monitors, television, or projection equipment. These technologies do not offer the quality of film due to bandwidth limitations.
In addition to the ability to transmit the necessary information via satellite, the received information must be displayed using a high quality projector, which has not previously been available. Moreover, implementation of a satellite based transmission and receiver system is costly and a radical change from current methods of film distribution and display. It is perceived that such a radical change may not be initially commercially acceptable.
Also, advances in digital technology have led to a revolutionary distribution concept whereby programming material is electronically stored in a digitized format, rather than on an optical film media. The digitized images may be distributed on various magnetic media or compact optical discs, or transmitted over wired, fiber optic, wireless, or satellite communication systems. A variety of DVD-ROM storage formats exist having storage capacities ranging from about 4.5 gigabytes (GB) to about 18 GB. The DVD-ROM storage formats that have a storage capacity greater than about 9 GB are implemented on dual-sided disks. As such, high storage capacity DVD-ROM disks must be manually turned over to access the stored information from the second side of the disk.
An average two hour movie having an average image compressed bit rate of about 40 Mbps for the image track and about eight Mbps for audio and control information requires approximately 45 GB of storage space. Thus, even if a high storage capacity DVD-ROM disk is implemented, a two-hour movie requires use of multiple DVD-ROM disks for adequate capacity.
Further, for playback, the average two-hour DVD-ROM movie requires information to be output at about 6 megabytes per second, or about 48 Mbps. Although some DVD-ROM devices exist advertise an 8 MB/sec transfer rate, the quality and reliability of such devices is unknown. Thus, there is no guarantee that such DVD-ROM devices can reliably sustain a 6 MB/sec transfer rate.
In order to reduce the data rate requirement for the storage of high quality electronic images, compression algorithms are being developed. One digital dynamic image compression technique capable of offering significant compression while preserving the quality of image signals utilizes adaptively sized blocks and sub-blocks of encoded discrete cosine transform (DCT) coefficient data. This technique will hereinafter be referred to as the adaptive block size discrete cosine transform (ABSDCT) method. The adaptive block sizes are chosen to exploit redundancy that exists for information within a frame of image data. The technique is disclosed in U.S. Pat. No. 5,021,891, entitled “Adaptive Block Size Image Compression Method And System,” assigned to the assignee of this application and fully incorporated herein by reference for all purposes. DCT techniques are also disclosed in U.S. Pat. No. 5,107,345, entitled “Adaptive Block Size Image Compression Method And System,” assigned to the assignee of this application and fully incorporated herein by reference for all purposes. Further, the use of the ABSDCT technique in combination with a Discrete Quad-tree Transform technique is discussed in U.S. Pat. No. 5,452,104, entitled “Adaptive Block Size Image Compression Method and System,” also assigned to the assignee of this application and fully incorporated herein by reference for all purposes. The systems disclosed in these patents utilize intraframe encoding, wherein each frame of an image sequence is encoded without regard to the content of any other frame.
Distribution of film information using a digital electronic format actually increases the potential for rapid, low-cost duplication without quality degradation. However, along with the “ease of duplication” associated with digital technology, there exists encryption techniques to ensure that the information is encoded in a way that prevents useful information from being distributed to unauthorized parties.
Technologies such as the ABSDCT compression technique, advanced projection equipment, and electronic encryption methods offer the possibility of a “digital cinema” system. Generally defined, digital cinema refers to the electronic distribution and display of high quality film programming which has been converted to a digital electronic representation for storage, transmission, and display purposes. A digital cinema system would overcome many of the limitations of the current film distribution process. A digital system would not be subject to the quality degradation over time experienced by celluloid film. Further, a digital system virtually eliminates the theft and illegal duplication of celluloid film, and further offers the possibility of implementing security measures within the digital system itself. However, a complete digital cinema system has not been developed by the motion picture industry or related arts.
Several issues and problems remain to be solved. New digital cinema systems require improved forms of protection to prevent theft from theaters. Theater complexes with multiple auditoriums have grown larger in an effort to provide a greater economic return, resulting in more complicated presentation schedules, and a larger number of locations showing a given film. This could require many additional electronic copies to be forwarded to theaters for presentation using current techniques, with associated complexity and operating costs.
Distribution channels and mechanisms are still defined by the older celluloid film copying and distribution techniques discussed above. New techniques are needed to take full advantage of proposed digital cinema processing, to reduce copying, provide faster releases to market, and updating products in release, while providing increased scheduling and distribution flexibility at reasonable cost. At the same time, some film producers, studios, and theater managers would like to have increased centralized control over releases and distribution, and to be able to expand into newer markets. For example, it is desirable to be able to supply films and other audio-visual presentations with alternative sound tracks to address increasing markets for multi-lingual or alternative language audiences, in a more cost effective manner.
What is needed is the integration of certain technology into an apparatus and method for the encoding, encryption, storage, and management of digital image and audio programming. These goals are achieved by the present invention in the manner described below.